A gas turbine generally includes a compressor, a combustion system, and a turbine section. Within the combustion system, air and fuel are combusted to generate an air-fuel mixture. The air-fuel mixture is then expanded in the turbine section.
Traditionally, combustion systems have employed diffusion combustors. In a diffusion combustor, fuel is diffused directly into the combustor where it mixes with air and is burned. Although efficient, the diffusion combustor is operated at a relatively high peak temperature, which creates relatively high levels of pollutants such as nitrous oxide (NOx).
To reduce the level of NOx resulting from the combustion process, dry low NOx combustion systems have been developed. These combustion systems use lean pre-mixed combustion. With lean pre-mixed combustion, air and fuel are pre-mixed in a fuel nozzle to create a relatively uniform air-fuel mixture. The fuel nozzle then injects the air-fuel mixture into the combustion chamber, where the air-fuel mixture is combusted at a relatively lower, controlled peak temperature.
Although such combustion systems achieve lower levels of NOx emissions, the fuel nozzles may be relatively likely to develop a flashback condition, wherein a flame stabilizes in one or more of the fuel nozzles. One common reason for a flashback condition in the fuel nozzle is an upstream flame propagation event, wherein flame propagates from an expected location in the combustion chamber upstream to the fuel nozzle. Another common reason for a flashback condition in the fuel nozzle is auto-ignition, wherein the air-fuel mixture in the nozzle independently ignites. Regardless of the cause, the flame may tend to stabilize within the fuel nozzle, which may damage the fuel nozzle or other portions of the gas turbine if the damaged hardware is liberated into the flow path.
To address this problem, combustion systems are normally designed to be flashback resistant, meaning to prevent a flame from stabilizing in the fuel nozzle. However, flashback resistant combustion systems have not been achieved for use with reactive fuels such as hydrogen, which are relatively more likely to experience flashback conditions than conventional fuels such as natural gas. The lack of flashback resistant combustions systems for reactive fuels limits their practicality, despite environmental benefits of their use.
What the art needs is systems and methods of detecting a flashback condition in a component of a gas turbine, such as a fuel nozzle of a dry-low NOx combustor burning hydrogen-rich fuel, so that appropriate corrective measures can be taken before damage is sustained.